Bone loss in patients with breast cancer receiving aromatase inhibitors and associated treatment strategies

Hormone-receptor-positive breast cancer in postmenopausal women is treated increasingly with aromatase inhibitors because of increased efficacy and reduced incidence of endometrial cancer compared with tamoxifen. However, aromatase inhibitor therapy increases bone turnover as a result of nearly complete oestrogen depletion, leading to increases in bone loss and fragility fractures that erode patients' functional independence and quality of life. Management of patients with aromatase inhibitor-associated bone loss (AIBL) is currently evolving and intervention strategies are under investigation. Although no treatments are specifically approved for AIBL, bisphosphonates are currently the intervention of choice for patients with low bone mineral density or evidence of rapid bone turnover, along with adequate calcium and vitamin D supplementation and a healthy lifestyle. In this setting, the majority of information available regarding bisphosphonate efficacy is from studies of intravenous zoledronic acid (4 mg) every 6 months. Data from four large international studies (three of identical design in postmenopausal women and one in premenopausal women) indicate that zoledronic acid is effective in the management of AIBL. Treatment algorithms based on risk factors and bone mineral density are under development, and the results of ongoing studies should help define optimal bone health management for patients undergoing aromatase inhibitor treatment for early breast cancer.